1. Field
One embodiment of the invention relates to an image data-outputting unit and a liquid crystal display device.
2. Description of the Related Art
Since a liquid crystal panel is of “a hold type” in which an image continues to be displayed at the same level for a one frame period (16 msec), a moving image blur occurs due to a response delay of liquid crystal in the liquid crystal panel of the hold type. On the other hand, since a CRT display, a surface-conduction electron-emitter display (SED) or the like is of “an impulse type” in which the light emission is made only for a moment of one frame period, no moving image blur occurs.
In recent years, the various kinds of methods have been proposed for the purpose of improving the moving image blur occurring in the liquid crystal panel. The techniques relating to these methods, for example, are disclosed in the Japanese Patent Kokai Nos. 2002-116743 and 2002-215111.
A liquid crystal display device disclosed in the Japanese Patent Kokai No. 2002-116743 is such that an image signal is written to a frame memory once for one vertical synchronous time period, an image signal is repeatedly read out from the frame memory twice for one vertical synchronous time period, and a voltage value corresponding the image signal thus read out is applied to each of corresponding display pixels of a liquid crystal panel. As a result, step responsibility of the display pixels is further improved in this case than in the case where the voltage value corresponding to the image signal is repeatedly applied three times at a rate of one time for one vertical synchronous period.
A liquid crystal display device disclosed in the Japanese Patent Kokai No. 2002-215111 includes a frame memory for storing therein an input image signal for one frame, a frame frequency-converting portion for converting a period of an image signal into half a frame period, and outputting the resulting image signal, and a signal switching portion for switching the image signal obtained through conversion of the frame period and a black display signal over to each other. Thus, an image to be displayed is displayed in the first half of the frame period, and a black signal is displayed in the second half of the frame period. As a result, it becomes possible to realize the display of a pseudo impulse type, and thus it is possible to improve degradation of an image quality due to the moving image blur.
However, according to the liquid crystal display device disclosed in the Japanese Patent Kokai No. 2002-116743, although the responsibility of the liquid crystal is improved, the moving image blur cannot be sufficiently improved. In addition, according to the liquid crystal display device disclosed in the Japanese Patent Kokai No. 2002-215111, although the moving image blur can be improved, the overall screen becomes dark because of reduction of a luminance. The displayed image is degraded depending on the kinds of images all the more because there are various displayed images such as the image having a low luminance and the image having a small motion.